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HelpTest Code LAB1930 Mexiletine, Serum
Additional Codes
MEX
Useful For
Assessing achievement of optimal therapeutic mexiletine concentrations
Assessing potential mexiletine toxicity
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Serum RedSpecimen Required
Patient Preparation: Specimens should only be collected after patient has been receiving mexiletine for at least 3 days. Trough concentrations should be collected just before administration of the next dose.
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1.5 mL
Collection Instructions:
1. Draw blood immediately before next scheduled dose.
2. Centrifuge and aliquot serum into a plastic vial within 2 hours of collection.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days |
| Ambient | 28 days | |
| Frozen | 28 days |
On-campus collections: Tube to 99 or deliver to University Extension Hospital Room EH318
Submission Container/Tube: Plastic vial, Refrigerated
Off-campus collections:
Centrifuge and aliquot within 2 hours.
Specimen to be stored/transported at Refrigerated temp.
Reference Values
Trough Value
0.5-2.0 mcg/mL: Therapeutic concentration
>2.0 mcg/mL: Toxic concentration
Day(s) Performed
Monday through Friday
CPT Code Information
80299
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| MEX | Mexiletine, S | 40779-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 9245 | Mexiletine, S | 40779-1 |
Interpretation
Optimal response to mexiletine occurs when the serum concentration is within the range of 0.5 to 2.0 mcg/mL (trough value).
Method Description
Protein is precipitated from serum and following centrifugation the supernatant is diluted and analyzed by liquid chromatography tandem mass spectrometry.(Unpublished Mayo method)
Report Available
2 to 5 daysSpecimen Retention Time
14 daysReject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Secondary ID
9245Forms
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.